This invention relates generally to the heat treatment of surface coverings such as wall coverings in order to impart certain characteristics to those surface coverings. More particularly, this invention relates to processes and apparatus for the rapid heat treatment of surface coverings in order to impart a texture or grain which may be either decorative, or serve some useful, practical purpose for the surface, when it is subsequently applied to a substrate.
Various kinds of thermoplastic sheet materials, which may be treated by heat applications, are used in large quantities today as wall coverings or surface coverings of some kind in order to impart to a substrate a particular color or texture. This is true of the individual panels forming the internal walls of aircraft cabins, for example, and the bulkheads thereof. That is, commercial airlines require that the interior surfaces of their particular aircraft have imparted thereto particular proprietary characteristics designating that airline. For example, the color may be selected to designate the airline, and the bulkheads arranged at the front of each aircraft cabin may have certain design characteristics or logos. In addition, private aircraft may have certain design characteristics as requested and/or desired by an individual owner in order to decorate a cabin for his or her specific purposes.
Thus, when aircraft are built and the substrate sections for forming the walls of the aircraft are formed, they are subsequently covered with coverings which impart certain appearance characteristics and/or textures to the overall appearance of the cabin once the coverings are applied and the individual wall sections are in place. Generally in the past, the wall coverings have been comprised of sheets of thermoplastic materials which are placed in presses for a period of minutes in order to impart graining and/or textures to the thermoplastic sheets prior to their subsequent heat adherance to the substrate wall panels forming the aircraft cabin walls. However, pressing the individual sheets of thermoplastic material under high heat conditions for several minutes has a tendency to degrade the components forming the thermoplastic material. That is, while thermoplastics have incorporated therein a large variety of additives developed over the years in order to maintain color integrity, flame retardancy, pliability, etc., long term exposure to high temperatures has a tendency to degrade the material such as, by, degrading the color of the material.
As discussed above, customers of aircraft have certain specific and very limited desires concerning the color and/or texture of the wall coverings for use in their particular aircraft. Any degrading during the processing of the wall coverings may have a tendency to affect the color to a degree where the materials cannot be used. Moreover, pressing each individual sheet of material for a period of minutes in order to impart the desired surface texture or graining takes time and of course increases the cost of preparing the wall coverings for subsequent application to the substrate involved. Also, when the treated coverings are subsequently applied by heat to substrate panels, the heat has a tendency to reduce the degree of desired texture previously imparted to the coverings.
With this invention, by contrast, methods and apparatus are provided for permanently and rapidly imparting surface characteristics to continuous webs of thermoplastic surface covering materials to impart thereto the desired texture and/or graining required in a matter of seconds, thus reducing long term exposure of the material to high temperatures and reducing the time involved in obtaining the desired characteristics. Moreover, the process and methods herein of high temperature embossing have the effect of increasing the integrity of the surface characteristic desired for subsequent heat application to a substrate. The above is achieved by utilizing conventional tenter frame apparatus for a continuous processing at high temperatures of a continuous web of thermoplastic material for such treatment.
The tenter chain apparatus of the invention utilizes a unique magnetic application in that one set of tentor chains carries individual magnets in each section thereof while the opposing chain is utilized to attract the magnets. Thus, the magnetic attraction serves to provide a continuous gripping of the web edges of a continuous thermoplastic sheet, which, therefore, may be carried through a processing apparatus. By doing so, the thermoplastic material is not exposed to any tearing from pin holes or clamps of any kind ordinarily associated with tenter frames.
The arrangement is such that the continuous web of material may pass through high temperature radiant heaters for imparting a high temperature level rapidly to the web of material which is, subsequently, simultaneously rapidly cooled while being passed over an embossing roll immediately after the application of heat. Subsequent to the cooling-embossing application, the continuous sheet of material passes over a cooling can which rapidly brings the embossed and/or textured and/or treated continuous web of material to ambient so as to fix the desired characteristic. Subsequent to the cooling, of course, the product is wound up for delivery for subsequent application of the covering material to a substrate.
Because of the rapid nature of the process and apparatus, in accordance herewith, the thermoplastic material is exposed to high temperatures for only three or four seconds. This reduces to a minimum any degradation of additives in the thermoplastic material including those for color, and/or flame retardancy and/or flexibility. Moreover, because of the high temperature rapid application of texture or graining to the thermoplastic material, the integrity thereof is maintained to a higher degree than is the case when such thermoplastic material has such texture or graining imparted in a press over a period of time of several minutes. With such long term exposure, lower temperatures must be used to avoid degrading the additives imparted to the thermoplastic formulation in the first place.
With the foregoing and additional objects in view, this invention will now be described in more detail, and other objects and advantages thereof will be apparent from the following description, the accompanying drawings, and the appended claims.
Before describing this invention in more detail, it may be well to note that a variety of thermoplastic materials may be utilized with the process and apparatus herein, including, for example, polyvinylfluoride, such as TEDLAR, a product of DuPont, polyvinyl chloride such as VHI Films, a product of General Tire Company which is a very high impact polyvinyl chloride film, polyvinyl chloride coated fabrics, acrylonitrile-butadiene-styrene terpolymer films, and combinations of the above.
As purely illustrative of apparatus which may be used for carrying out the process of this invention, one may note the attached drawings in which conventional tenter frame apparatus has been modified according to this invention to provide the new processing characteristics and conditions for this invention, including the utilization of magnetic attraction in tenter frames together with the positioning of specific radiant heater apparatus, and an arrangement for removing the margins or edges of the continuous web of material being processed, which margins or edges were utilized to maintain the continuous sheet or web and carry it through the apparatus to the point of the embossing rolls. At this point, the edges or margins are slit from the continuous web of material which passes around the embossing roll. Thus, once the magnetic attraction of the tenter chains leave the material being treated, the edge margins, which were held by the tenter chains are also removed at the same time.